The M197 electric cannon is a three-barreled electric Gatling-type rotary cannon used by the United States military and JSDF.
The M197 electric cannon was developed primarily for use by United States Army helicopter gunships. Development began in 1967 after experience in the Vietnam War revealed the inadequacy of the 7.62 mm Minigun for gunship use. The M197 is essentially a lightened version of the General Electric M61 Vulcan cannon, with three barrels instead of six. Its maximum rate of fire is one quarter that of the Vulcan, largely to limit its recoil for light aircraft and helicopter use. It shares the Vulcan's M50 and PGU series 20 mm ammunition.
These chain guns often seen mounted on JSDF attack helicopters.